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Tutorials › PostgreSQL Essentials › EXPLAIN and Performance

EXPLAIN and Performance

6 min read
EXPLAIN ANALYZE shows how PostgreSQL executes a query. Look for Seq Scan on large tables — it usually means you need an index. Compare estimated vs actual row counts to find planner mistakes causing slow queries.

Query Performance

-- Basic plan
EXPLAIN SELECT * FROM users WHERE age > 25;

-- With actual timings
EXPLAIN ANALYZE SELECT * FROM users WHERE age > 25;

-- Look for:
-- Seq Scan (no index) vs Index Scan (uses index)
-- Rows Removed by Filter (high = needs index)
-- Total cost

The goal: low cost, Index Scans over Seq Scans.